Diesel and other engine-powered generators (gensets) used as power sources (e.g., as stand-by or back-up power sources) are typically periodically tested to ensure their availability and reliability when needed. During these tests the generator can be connected to a load bank—a device that develops an electrical load and dissipates the power generated by the genset. The exhaust from the engines powering gensets is sometimes processed by aftertreatment systems to reduce emissions. Exhaust aftertreatment systems of these types are disclosed, for example, in the Pierz et al. U.S. Patent Application Publication No. 2010/0186373 and the van Niekerk U.S. Patent Application Publication No. 2012/0121475. There remains, however, a continuing need for improved exhaust after treatment systems.